A communication system may use in-phase and quadrature-phase clock signals (e.g., four clock signals, each offset in phase by 90 degrees) to receive and/or transmit signals. In some cases, a poly-phase filter using passive Resister-Capacitor (RC) components may be used to generate these clock signals. Such clock signals, however, may not be accurate over a relatively wide frequency band (e.g., the clock signals might only be accurate at or near a single frequency). As another approach, a ring oscillator may be used to generate the clock signals. In this case, the amount of jitter present in the clock signals may be unacceptable.